HELP HELP HELP!!!

Bigsnow · Feb 8, 2025

Everyone, I have a sick '94 that needs help.

I was driving a while back and my engine started running poorly. I made it home by high revving the engine but it died immediately after getting in the garage (idle.)

Engine can start and run, barely, and seems to be running on only a few cylinders.

I've tried:
Replaced headgaskets no change
Replaced Timing sprockets/ chain (thought it may have skipped a tooth. It was sloppy, and glad I changed it) no change
Replaced: camshaft sensor 2X, crank sensor, MAP sensor, ignition coil packs, BOTH ECU and the PCM. no change
Drained tank, fresh gas. no change
Fuel pump and filter are fairly new. I can hear it pump up at key ON.
Ignition wires are good, (And, a bunch going bad at the same time shouldn't happen.)
I've got spark on all cylinders.
Checked a few injectors. Screens are clear and they seem to function properly.

I am completely stumped.

It starts, and I can rev it up.... but it's definitely not running on all cylinders. Feels, sounds like three. The passenger-side exhaust doesn't even heat up. Driver exhaust does.

NOTHING I've done has made any change whatsoever.

HELP!!!!

daveg · Feb 9, 2025

No OBDI codes?
Did you try the Cycling Key trick to read them?

99RT10GTS · Feb 9, 2025

Weird, It does *sound* like a fuel issue. Did you change the fuel pump? Have you put a gauge on the fuel rail(scharder valve) to see if you are at 55PSI?

Fuel injectors- I would still pull them all and get them cleaned a checked professionally. Maybe even install Gen 2 injectors(red tops) to have slightly better fuel flow.

Viper Specialty · Feb 9, 2025

Where are you located?

Bigsnow · Feb 9, 2025

I live in Atlanta.

I have a code reader. I had one code for the MAP sensor at first. I changed that, as well.

I can only assume I have a wiring issue.

Anyone point me towards a pinout of PCM/ECU connectors?

Thanks to the responders!

daveg · Feb 9, 2025

I have a 92-96 PDF parts manual but i doubt it has pinouts..
Is the car stock?

TEALLIFE · Feb 10, 2025

any chance the crank pulley spun?

Viper Specialty · Feb 10, 2025

Bigsnow said:
I live in Atlanta.

I have a code reader. I had one code for the MAP sensor at first. I changed that, as well.

I can only assume I have a wiring issue.

Anyone point me towards a pinout of PCM/ECU connectors?

Thanks to the responders!

Honest opinion, this needs to go to a shop with the proper scan tools that can check all of the engine I/O and see if everything is functioning properly electrically. Wish you were closer, this is exactly the stuff that I love... but trying to do it remotely is a nightmare. SO many things were "guess and checked" that the diag tree is a complete mess and needs to be started over.

daveg · Feb 10, 2025

TEALLIFE said:
any chance the crank pulley spun?

Hopefully not. If it did and the snout is bad, he will have to at a minimum Pin it.

Bonkers · Feb 11, 2025

Also remember, "New" does not mean "Not Broken." I just went
through four brand new starters on my Excursion before i got
one that could crank the engine.

Id recheck the "new" stuff just to be sure, focusing on whether you
have fuel pressure. It could be something as simple as a clogged fuel
line or clogged cat.

eckeph · Feb 11, 2025

Check the spark plugs on the passenger side after you ran it for a while. If they are dry then you probably have an issue with the injectors not getting any fuel or that they do not open. Check the fuel rail so it's not clogged. I seem to recall that all the injectors on each side goes through one connector per side, check that connector so it's properly attached.

kblake905 · Feb 11, 2025

Bigsnow said:
Everyone, I have a sick '94 that needs help.

I was driving a while back and my engine started running poorly. I made it home by high revving the engine but it died immediately after getting in the garage (idle.)

Engine can start and run, barely, and seems to be running on only a few cylinders.

I've tried:
Replaced headgaskets no change
Replaced Timing sprockets/ chain (thought it may have skipped a tooth. It was sloppy, and glad I changed it) no change
Replaced: camshaft sensor 2X, crank sensor, MAP sensor, ignition coil packs, BOTH ECU and the PCM. no change
Drained tank, fresh gas. no change
Fuel pump and filter are fairly new. I can hear it pump up at key ON.
Ignition wires are good, (And, a bunch going bad at the same time shouldn't happen.)
I've got spark on all cylinders.
Checked a few injectors. Screens are clear and they seem to function properly.

I am completely stumped.

It starts, and I can rev it up.... but it's definitely not running on all cylinders. Feels, sounds like three. The passenger-side exhaust doesn't even heat up. Driver exhaust does.

NOTHING I've done has made any change whatsoever.

HELP!!!!

Could be a plugged Catalytic converter?

TEALLIFE · Feb 11, 2025

eckeph said:
Check the spark plugs on the passenger side after you ran it for a while. If they are dry then you probably have an issue with the injectors not getting any fuel or that they do not open. Check the fuel rail so it's not clogged. I seem to recall that all the injectors on each side goes through one connector per side, check that connector so it's properly attached.

Its easy to check with an infrared thermometer on the header. If there's no fuel, the header from that cylinder will be colder

Copperhd · Feb 11, 2025

You said you had a MAP sensor fault, which code was it? I would check that circuit or check for a vacuum leak to the MAP sensor. Another thing to remember is anything that causes the engine to run poorly may throw a MAP sensor voltage high code, which means engine vacuum is low.

haneifk · Feb 11, 2025

Maybe try a compression test and see what numbers you're getting.

eckeph · Feb 12, 2025

TEALLIFE said:
Its easy to check with an infrared thermometer on the header. If there's no fuel, the header from that cylinder will be colder

He already wrote that the headers on the passenger side was cold. I'm trying to determine if the cylinders gets fuel or not. If the spark plugs are wet then it might be a problem with the ignition. If they are dry then there might be a problem with the fuel. Simple!

TEALLIFE · Feb 12, 2025

eckeph said:
He already wrote that the headers on the passenger side was cold. I'm trying to determine if the cylinders gets fuel or not. If the spark plugs are wet then it might be a problem with the ignition. If they are dry then there might be a problem with the fuel. Simple!

sorry, missed that. good place to start. Weird that one side is overheating and one side is completely dead.

Viper Specialty · Feb 12, 2025

Just to throw it out there......

Early Gen-1 is known for cracked intake manifolds' internal fuel rail, which would flood every cylinder near it and run like general hot garbage.

If its a 4-rib manifold, thats very real possibility.

99RT10GTS · Feb 12, 2025

If its a 4-rib manifold, that's very real possibility.

I have a good one of those for sale...........

Bigsnow · Feb 15, 2025

UPDATE:

Thanks for all the GREAT ideas.

The code reader reports NO codes currently. So, I have high confidence sensors are good. It's probably not the crank pulley because I just changed the timing set. (And the car started running poorly while in stop-n-go traffic, low load demand.) Cracked intake? It IS a 4 rib, but I didn't see any problems while changing the head gaskets. A clog maybe. But, I've noticed #1 and #2 cylinders are firing. Also, no excess fuel smells and the exhaust is dry (except for minor condensation)

I'm hoping I may have found the problem. I measured the fuel pressure and it's reading 30 PSI at key-on. I have a sh*t fuel pressure gauge and am getting a loaner to re-test.

Regardless, I've ordered a new pump and filter.

I will confirm the low pressure and most likely swap out the pump/filter. About 8 years ago, I took the tank out, and I think I remember that I might be able to access the filter and pump from underneath without having to pull the tank.

Can anyone confirm this?

After new pump/filter and with no change, I'll try the pressure regulator.

Again, thanks for the brain-storming!

Mark Snow

eckeph · Feb 15, 2025

Bigsnow said:
The passenger-side exhaust doesn't even heat up. Driver exhaust does.

This statement that you made in your original post (if true) points the blame at one very particular place; Fuel rail/injectors passenger side. This considering all the things you state that you have done already.
Or... reading your statement again... I assumed that it meant that all of the cylinders where cold, as in not firing, maybe you mean that the collector is "cold"? Which could mean that some cylinders are firing? Can you please confirm this?

99RT10GTS · Feb 15, 2025

The fuel rail is internal on the intake. I have seen them fail on the 4 ribs a lot more then the 3 ribs. Good chance it is the intake.

white out · Feb 17, 2025

Bigsnow said:
The code reader reports NO codes currently.

Mark Snow

My '96 dropped a valve seat and didn't throw a code. lol

TEALLIFE · Feb 17, 2025

white out said:
My '96 dropped a valve seat and didn't throw a code. lol

90s tech isn't the best for trusting their codes LOL

Bigsnow · Feb 22, 2025

UPDATE: I'm still at it. Fuel pressures are good. At 55 PSI at start and while (very roughly) running. (** Interesting note - my '94 has the fuel pump on the back trunk wall mounted next to the fuel filter. The parts diagram has the fuel pump module IN the tank. Thinking mine is a late '93 design? Doesn't matter where it is, as long as it works!**)

Going back to double check all the ignition parts. Spark on all cables, correct wiring, etc... Still crazy.

Fresh update: Ok, Dummy move. I had #5 and #7 wires crossed. Running far better but still has awful miss and stalls at idle. I think I have two non firing cylinders. I'm cleaning, and then replacing the IAC valve next.

Thanks for following my journey. I WILL solve it.

TEALLIFE · Feb 24, 2025

Bigsnow said:
UPDATE: I'm still at it. Fuel pressures are good. At 55 PSI at start and while (very roughly) running. (** Interesting note - my '94 has the fuel pump on the back trunk wall mounted next to the fuel filter. The parts diagram has the fuel pump module IN the tank. Thinking mine is a late '93 design? Doesn't matter where it is, as long as it works!**)

Going back to double check all the ignition parts. Spark on all cables, correct wiring, etc... Still crazy.

Fresh update: Ok, Dummy move. I had #5 and #7 wires crossed. Running far better but still has awful miss and stalls at idle. I think I have two non firing cylinders. I'm cleaning, and then replacing the IAC valve next.

Thanks for following my journey. I WILL solve it.

Which 2? Could it be a bad coil?

Viper Specialty · Feb 24, 2025

Bigsnow said:
UPDATE: I'm still at it. Fuel pressures are good. At 55 PSI at start and while (very roughly) running. (** Interesting note - my '94 has the fuel pump on the back trunk wall mounted next to the fuel filter. The parts diagram has the fuel pump module IN the tank. Thinking mine is a late '93 design? Doesn't matter where it is, as long as it works!**)

Going back to double check all the ignition parts. Spark on all cables, correct wiring, etc... Still crazy.

Fresh update: Ok, Dummy move. I had #5 and #7 wires crossed. Running far better but still has awful miss and stalls at idle. I think I have two non firing cylinders. I'm cleaning, and then replacing the IAC valve next.

Thanks for following my journey. I WILL solve it.

Dude.

STOP.

Find the actual problem, and STOP BUYING PARTS AND CHANGING THINGS. You have spent so much time and money swapping things at this point, that you could have bought the proper diagnostic tools already 10x over, or brought someone like me TO YOUR HOUSE from across the country, or moved your car here and back.

Sorry for being blunt, but things like this drive me insane. You dont solve problems by just changing things until you stumble onto the answer!

This reminds me of a job I had last year. Dealership did a service on a Gen-1, crossed some wires. SIMPLE. Started replacing all sorts of things chasing a simple problem. Found the plug wires being swapped, switched it back... thought they had it solved, but misfires remained. Brought me in, SWORE they did a proper job, and wouldnt re-check their work. Had me do base diag, everything came back fine. Started replacing modules, even though they checked out fine. Started replacing injectors, even though they were fine... still no dice. I told them to dig back through the engine, never heard back. Found out months later, they put in the wrong damn pushrod length while changing things that didnt need to be changed because of the plug wire based misfire, and created a load of new misfires in the process that would never be diagnosable without disassembly. In short, they made me a one-legged man in an ass-kicking contest because they didnt leave it the F alone before I got my hands on it.

LEARN from their mistakes, and learn from your own. STOP. Re-check everything. Unless you find an actual problem, STOP CHANGING PARTS. In fact, PUT THE OLD ONES BACK IN if they are still good condition, and save the new ones as actual new spares.

Bigsnow · Feb 24, 2025

Well hell. Haven't you ever had a puzzle you wanted to solve? I'm not going to **** out. Yes, I made a mistake with crossed wires. Good grief. Happy to drive you crazy because you're so smart.

I've given TONS of explanation here. What's your opinion?

TEALLIFE · Feb 24, 2025

Viper Specialty said:
Dude.

STOP.

Find the actual problem, and STOP BUYING PARTS AND CHANGING THINGS. You have spent so much time and money swapping things at this point, that you could have bought the proper diagnostic tools already 10x over, or brought someone like me TO YOUR HOUSE from across the country, or moved your car here and back.

Sorry for being blunt, but things like this drive me insane. You dont solve problems by just changing things until you stumble onto the answer!

This reminds me of a job I had last year. Dealership did a service on a Gen-1, crossed some wires. SIMPLE. Started replacing all sorts of things chasing a simple problem. Found the plug wires being swapped, switched it back... thought they had it solved, but misfires remained. Brought me in, SWORE they did a proper job, and wouldnt re-check their work. Had me do base diag, everything came back fine. Started replacing modules, even though they checked out fine. Started replacing injectors, even though they were fine... still no dice. I told them to dig back through the engine, never heard back. Found out months later, they put in the wrong damn pushrod length while changing things that didnt need to be changed because of the plug wire based misfire, and created a load of new misfires in the process that would never be diagnosable without disassembly. In short, they made me a one-legged man in an ass-kicking contest because they didnt leave it the F alone before I got my hands on it.

LEARN from their mistakes, and learn from your own. STOP. Re-check everything. Unless you find an actual problem, STOP CHANGING PARTS. In fact, PUT THE OLD ONES BACK IN if they are still good condition, and save the new ones as actual new spares.

pretty much this.

daveg · Feb 24, 2025

Viper Specialty said:
......they made me a one-legged man in an ass-kicking contest.

LOL, I must remember that quote next time I talk to my Boss....

HELP HELP HELP!!!

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